Process for making oil from aqueous reactive sludges and slurries

ABSTRACT

A process for making low sulfur oil by reacting aqueous reactive sludges and slurries with hot, pressurized carbon monoxide and hydrogen (synthesis gas) wherein the wastes are first concentrated by coking in the liquid phase under a pressure of 300 to 3000 psig at a temperature of 400 DEG  to 550 DEG  F for from 5 minutes to 2 hours.

CROSS REFERENCE TO COPENDING APPLICATION

This application is a division of co-pending, coassigned applicationSer. No. 532,967 filed Dec. 16, 1974, now U.S. Pat. No. 4,030,981 issuedJune 21, 1977.

BACKGROUND OF THE INVENTION

This invention is concerned with a process for making low sulfur oilfrom sewage sludge.

The Bureau of Mines Report PB 203,669, entitled "Converting OrganicWastes to Oil", describes the reaction of carbon monoxide and water withvarious biological wastes containing cellulose, and other carbohydrates.These wastes include wood wastes (largely cellulose and liquid), sewagesludge and other urban wastes (mostly cellulose and other carbohydratesplus proteins and fats), and agricultural wastes such as cow manure.They have found that by reaction of these materials with CO and water alow sulfur oil can be produced.

One difficulty with this process as applied to sewage is that the sludgeis so dilute that the reactor employed for the reaction of the CO andwater with the sludge must be very large.

SUMMARY OF THE INVENTION

To eliminate the above-outlined problem, the present invention providesa method and means for concentrating reacting solids by coking at atemperature of 400° to 550° F. in the liquid phase under a pressure of300 to 1200 psig for 5 minutes to 2 hours to produce a concentrate whichis then fed to a CO-water reactor. The solids are concentrated byremoving 50 to 99 percent of the liquids comprising the sludge andtreated with carbon monoxide at a pressure of 500 to 5000 psig and atemperature of 500° to 750° F. to form gases, solids and oil.

BRIEF DESCRIPTION OF THE DRAWING

The invention is illustrated diagrammatically by a single FIGURE whichshows one possible apparatus for carrying out the invention.

In the practice of the invention, primary sludge from a sewage plant ispumped up to system pressure (around 400 psig) by pump 10 then throughheat exchanger 1 and heater 2 where it is heated to around 450° F. andthence to coke drum 3 where coke 12 settles to the bottom. Grease 14rises to the top and is skimmed off through valve 13. Gas is taken offthrough line 6 and recombined with coker effluent removed through line7. Air is injected to the coker effluent in line 16 through inlet 18 toburn out remaining chemical oxygen demand (COD) of the effluent, andfinally the oxidized coker effluent is passed through heat exchanger 1in heat exchange with fresh feed. Wet coke slurry 12 is pumped throughline 20 after addition through inlet 22 of Na₂ CO₃ in water as catalyst,to the reactor 4 where it reacts with hot synthesis gas introducedthrough line 29. The oil produced and water and gas pass from the top ofvessel 4 through line 24 and the oil and water are condensed and thenseparated in separator 5. A portion of the gas is vented through line 26and the remainder recycled through line 28 to reactor 4. Water and oilare removed from the separator through outlet 30. Solids are removedfrom the bottom of vessel 4 through trap 32 and may be reacted in knownmanner to produce synthesis gas and a residue which is useful as afertilizer and soil conditioner.

In an example of the successful practice of the process, there werecoked in liquid phase at 450° F and 400 psig 2700 grams of sewage sludgefrom the primary settler of the Beacon, New York sewage plant. Theyields from the coking operation were as follows:

    ______________________________________                                        Gas: 2.6 g. (0.09 wt. %)                                                                        Composition (Mol. %)                                        ______________________________________                                                        Butylenes 0.2                                                                 Propylene 0.9                                                                 H.sub.2 S 0.3                                                                 H.sub.2   0.4                                                                 CO.sub.2  98.2                                                Grease: 5.4 g. (0.2 wt. %)                                                                      72% carbon                                                  Coke Slurry: 205 g. (7.5 wt. %)                                                                 on a dry basis represents                                                     54 g. (2.0 wt. % charge)                                                      Dry Coke Analysis                                                             41.6 wt. % carbon                                                              6.1 wt. % hydrogen                                                           31.1 wt. % ash                                              Liquid Effluent from Coker (92.2 wt. %)                                       ______________________________________                                    

The charge to the coker had a COD of 60,000 mg. O₂ /liter and theeffluent from coker had 14,179 mg. O₂ /liter COD for a COD reduction at76.4%.

It can be seen from the above that the COD of the raw sewage had beenreduced by 76.4% with the COD reduction being accounted for by the gas,grease and coke slurry produced.

The coke clurry, representing 7.6 weight percent of the sewage sludge,was transferred to an autoclave and pressured with 650 psig of CO andthen run at 575° F. for 2 hours. A pressure of 2900 psig was developed.The autoclave was opened and the viscous liquid was removed with the aidof benzene and extracted in an extractor with benzene to yield 18.5grams of oil (after removal of benzene) and 11.3 grams of solids (dry,benzene-free).

    ______________________________________                                                                                Gross                                                                         Heat of                                                    Wt. %         Wt.  Combus-                               Wt. %      Wt. %     Nitro-  Wt. % %    tion                                  Carbon     Hydrogen  gen     Sulfur                                                                              Ash  BTU/lb.                               ______________________________________                                        Oil                                                                           Analysis                                                                             74.4    10.7      2.1   0.22  --   16,296                              Solid                                                                         Analysis                                                                             16.4    1.8       0.6   0.64  75.2.sup.a                                                                          3,018                              ______________________________________                                         .sup.a Ash Analysis from Solid                                                 3.1% phosphorus                                                              39.1% silica                                                                  0.41% potassium                                                          

There were 54 grams of solids available for the CO-water reaction, or,by analysis, 22.4 grams of carbon available for the reaction.

61.5% of the carbon was converted to low sulfur oil.

8.3% of the carbon remained in the solids.

The above data shows that by concentrating the sewage solids, reactorvolume of vessel 4 is reduced by about 90% over that required if the rawsewage alone were treated. Also, the amount of water in reactor 4 iskept to a minimum so that the heat load and the energy requirements arereduced.

While the present invention has been exemplified by reference to thetreatment of sewage sludge, the same is not limited to such materialbut, rather, can be applied to the treatment of various reactive sludgesand slurries which contain cellulose, starches and relatedcarbohydrates.

Various catalytic agents are suitable for improving the conversion stepof the process. Such agents include NaHCO₃, K₂ CO₃ and KHCO₃.

What is claimed is:
 1. A process for making low sulfur oil from anaqueous charge containing cellulose and other carbohydrates comprisingcoking said charge at a temperature in the range of 400° to 550° F undera pressure of 300 to 1200 psig for 5 minutes to 2 hours to form anaqueous slurry containing cokes solids; removing from 50 to 99 percentof the liquid from said slurry; contacting the thus concentrated slurrywith hot pressurized synthesis gas at a pressure of between about 500 to5000 psig at a temperature of between 500° to 750° F to form a lowsulfur oil, gases and carbon and inorganic solids and separating saidoil from said carbon and inorganic solids and gases.
 2. The process ofclaim 1 wherein said charge consists of sewage sludge.
 3. The process ofclaim 1 wherein a catalytic agent of the group of Na₂ CO₃, NaHCO₃, K₂CO₃ and KHCO₃ is added to said concentrated slurry.